The carotid sinus reflex is maintained in patients receiving beta adrenergic blockers for hypertension. Clinical studies suggest that these drugs might reset the sinus to a lower pressure threshold. Studies in animals suggest that propranolol, a representative of this class of drugs, enhances the carotid sinus reflex by decreasing sinus wall distensibility. This would tend to increase the pressure load on the receptors at any given sinusal pressure. Stimulation of superior cervical ganglion also decreases sinus wall destensibility and enhances depressor nerve activity. It is conceivable that the antihypertensive drugs may interact with the muscle-nerve response and contribute to the resetting of the sinus pressure threshold. We intent to detemine the effect in the spontaneous hypertensive rat of section of the superior cervical ganglion on pressure before, during and after chronic administration of 3 beta adrenergic antagonists, each with varying anesthetic and beta blocking activities. The three drugs to be used are the d and l isomers of propranolol and sotalol.